| Transmission conductor is easy to form ice in the weather of freezing rain, it willproduce self-excited vibration of low frequency and high amplitude under a certain windspeed, known as galloping. Iced conductor becomes non circular cross section, it make theforce and flow field complex surrounding conductor. The aerodynamic characteristics of icedconductor are an important factor of galloping research problem. To obtain aerodynamiccharacteristics mainly through wind tunnel test and numerical simulation, due to randomnessof the problem of iced conductor galloping, test time consuming and high cost, computationalfluid dynamics (CFD) method could make up for the shortage of the wind tunnel test, also hasthe advantages of simulate the complex flow field, can be used for iced conductor onaerodynamic studies.The analysis of the current galloping phenomenon, generally using the quasi statichypothesis, it takes aerodynamic force from the static simulation or test at dynamic iced andgalloping conductor. Because the iced conductor galloping is the coupling of verticalvibration and torsion vibration, the actual aerodynamic force changes with time and otherfactors from hour to hour, the quasi static hypothesis is not applicable, it is necessary to adoptthe method of dynamic test or simulation to examine dynamic aerodynamic coefficients of theiced conductor. But acquiring dynamic aerodynamic coefficient need more complicateddevice, and the motion parameters are difficult to determine when galloping, especially largerspan and galloping amplitude. This paper uses the numerical method, based on softwareFluent redevelopment, the user-defined function described the track of conductor gallopingand dynamic mesh technology were used to realize the fluid and solid coupling from the weakcoupled model, research the changing rule of aerodynamic coefficient of iced conductor undertransverse vibration, analysis the galloping amplitude, frequency and the reverse effects onaerodynamic force.For iced single conductor under different attack angles, to simulate the static aerodynamiccharacteristics and comparing with the existing results of wind tunnel testing, and verify thereliability of numerical simulation. Based on this calculation model, the further study on thedynamic aerodynamic characteristics of iced conductor under the lateral vibration, analysisthe influence of galloping amplitude and frequency on dynamic aerodynamic force, andconsidering the dynamic aerodynamic characteristics when the iced conductor on thetransverse vibration and torsion vibration. The results showed that:(1) the dynamic and staticaerodynamic coefficients have the same variation law. Dynamic resistance coefficient isgreater than the static values, they basically have same gap; dynamic lift and reversecoefficient close to their static values, but the gap is large in the two peaks.(2) The resistanceand lift coefficients significantly increased with the increase of galloping amplitude,especially the lift coefficient increases exponentially; when vibration frequency increases, the aerodynamic coefficient also increase, but the frequency effect on the dynamic aerodynamicforce is less than that of amplitude.(3) The torsion vibration has certain influence on themagnitude of dynamic aerodynamic coefficient; compared with only the transverse vibrationgalloping, the dynamic resistance and lift coefficients changing with time more intense, andthe dynamic resistance coefficient of vibration frequency has change.For iced quad bundled conductor to simulate the static and the dynamic aerodynamiccharacteristics on transverse vibration, and the static simulation results comparing withexperimental results. The influence of conductor wake on aerodynamic force is analyzed, theeffect of the galloping amplitude, frequency and the conductor spacing on dynamicaerodynamic characteristics is studied. The results showed that:(1) The dynamic aerodynamiccoefficients of four root conductors under the lateral vibration are greater than that of thestatic, both have the same change rule, the gap between static and dynamic of windward sideconductors is smaller than the leeward side conductors; the aerodynamic coefficient gap of thewindward and leeward side is smaller than that of in static, but because of the influence of thewake on the aerodynamic dynamic coefficient of leeward side conductors is more intensealong with the change of time; four conductors will influence each other.(2) The influence ofgalloping amplitude and frequency on dynamic aerodynamic coefficients of quad bundledconductors is same as that of the single conductor. With the galloping amplitude andfrequency increases, the dynamic aerodynamic coefficient increases, the influence of theamplitude is greater than that of frequency.(3) The conductor spacing is smaller, the wakeeffect is greater, and the aerodynamic coefficients of leeward side conductors are smaller.According to the simulation results of the dynamic aerodynamic characteristics ofcrescent iced single and four split conductor, when the static aerodynamic coefficients areused to prediction of the critical wind speed of conductor break and tower loads caused bylarge span galloping in engineering, the results tend to unsafe. The effects of dynamicaerodynamic coefficients on galloping should consider. |
